The present invention relates to a welding head. In particular, the present invention relates to a welding head for friction stir welding applications.
Friction stir welding is a process of welding component parts together using friction heat generated at a welding joint to form a plasticized region which solidifies joining workpiece sections. A welding head is used to generate friction heat along a welding joint. The welding head includes a welding probe which is inserted into a joint between workpiece sections. The probe includes a pin that is inserted into the joint and a shoulder which is urged against an upper surface of the workpiece. The pin and shoulder spin to generate friction heat to form a plasticize region along the joint for welding operation.
For welding operation, a workpiece is supported by a rigid table or backplate typically formed of a steel plate. Rigid backplate stabilizes the actuation force of the upper shoulder to maintain the integrity of the workpiece so that the workpiece does not bend or deform under the load. To maximize strength of the joint between workpiece sections, the welded portion should extend the entire thickness of the workpiece. To assure that the weld extends the entire thickness, sufficient friction heat must be generated between upper and lower surfaces of the workpiece so that the plasticized region extends between upper and lower surfaces of the workpiece .
Typically, the thickness of a workpiece can vary along the joint. Variations in the workpiece thickness can vary pin depth or extension into the workpiece joint. If pin depth does not extend sufficient thickness, the plasticized region does not extend the entire thickness of the workpiece causing stress notches in the joint. For a smaller thickness, pin can extend too close to the backplate so that workpiece becomes joined to the backplate as a result of the welding operation. These and other problems are addressed by the present invention.